Analysis of station blackout accidents for LWRs

Station Blackout, the loss of all ac power in a nuclear power plant, is a Nuclear Regulatory Commission (NRC) unresolved safety issue. This paper summarizes the work done to resolve this issue. The analysis can be conveniently divided into three parts: (1) loss of offsite power-the results covered include generic initiating event frequency and duration of loss of offsite power and a summary of important factors affecting the initiating event frequencies and restoration probabilities; (2) loss of onsite ac power - the results covered include the unavailability of different diesel generator configurations, dominant factors affecting their unavailabilities, examples of sensitivities performed on the dominant factors, and examples of system undependability for these diesel generator configurations; and (3) accident sequence analysis - the results covered include dominant accident frequencies for the different generic classes of plants identified, dominant factors affecting sequence frequencies, examples of sensitivities done on the dominant factors, and a discussion of some of the most important features